This application pertains to the art of fluid signal regulation and modulation. The invention finds particular application in automotive pneumatic pressure, particular vacuum, control systems. More specifically, the invention finds application in modulating exhaust gas recirculation (EGR) controlling vacuum signals as a function of engine speed (RPM) as well as throttle position. It is to be appreciated, however, that the invention is applicable to controlling fuel flow as a function of engine speed and altitude and for amplifying, regulating, combining, or modulating fluid signals in other control applications.
Heretofore, automotive EGR valves on diesel engines have been opened progressively with increasing engine throttle position only. Commonly on diesel engines, EGR control system include a throttle position to vacuum signal transducer which produces a regulated signal that varies inversely with throttle position. The regulated signal is used to operate a vacuum motor which, in turn, operates the EGR valve.
Commonly, kinetic/pneumatic transducers are utilized in automotive and other applications for converting variations in mechanical energy into variations in a vacuum signal. Such transducers are shown, for example, in the temperature regulator assemblies illustrated in U.S. Pat. Nos. 4,245,780, 3,831,841, and 3,770,195 all to R. J. Franz. In these temperature regulator assemblies, the mechanical force from a bi-metalic element modulates a vacuum signal to produce a vacuum output which varies as a function of temperature. Another application for such transducers is for controlling an automotive blend-air system, such as illustrated in U.S. Pat. No. 3,476,316 to R. J. Franz. The blend-air control system includes a cam which is moved in response to engine temperature to provide a vacuum signal which varies with engine temperature. The vacuum signal is used to adjust the position of a blend-air door that varies the percentage of air passing to the carburator through a heat exchanger.
The present invention provides a modulator or regulator valve which produces an output signal that is a function of two variables, thus overcoming the limitations associated with single variable control systems.